<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title></title>
  <style>
    body {
      width: 1200px;
    }

    div {
      width: 400px;
      height: 200px;
    }

    .top {
      background-color: red;
    }

    .middle {
      background-color: orange;
      position: relative;
      top: 100px;
      left: 100px;
    }

    .bottom {
      background-color: yellow;
    }
  </style>
  <link href="css/style.css" rel="stylesheet">
</head>

<body>
  <div class="top">最上面的div</div>
  <div class="middle">中间的div</div>
  <div class="bottom">最下面的div</div>

</body>

</html>
